Coating thickness gauge

Abstract

A coating thickness gauge for measuring the thickness of a coating on a surface of a can is described. The gauge comprises a probe head and a probe head locating mechanism. By employing the probe head locating mechanism the probe head can be easily orientated relative to the surface of a can. The ability to select and fix the measurement orientation of the probe head provides the coating thickness gauge with enhanced flexibility such that it can be employed to take measurements from all surface sections of the can, both interior and exterior. This ability is not dependent on the experience, knowledge or skill of a particular operator. As a result the gauge provides for a fast means of measuring the thickness of a coating which can be used within an in line feedback system, on a commercial scale.

1 ) A coating thickness gauge suitable for measuring the thickness of a coating on a surface of a can, the gauge comprising a probe head located at a distal end of a probe arm, the probe arm having a longitudinal axis, and a probe head locating mechanism wherein the probe head locating mechanism provides a means for selecting and fixing a measurement orientation of the probe head relative to the longitudinal axis.  
   
   
       2 ) A coating thickness gauge as claimed in  claim 1  wherein the gauge further comprises an electromagnetic wave source suitable for producing an interference pattern following reflection of the electromagnetic waves from the coating on the surface of the can.  
   
   
       3 ) A coating thickness gauge as claimed in  claim 2  wherein the source of electromagnetic waves comprises a white light source.  
   
   
       4 ) A coating thickness gauge as claimed in  claim 2  wherein the source of electromagnetic waves comprises a monochromatic light source.  
   
   
       5 ) A coating thickness gauge as claimed in  claim 2  wherein the gauge further comprises an optical fibre employed to couple the electromagnetic wave source to the probe head.  
   
   
       6 ) A coating thickness gauge as claimed in  claim 5  wherein the optical fibre is also arranged to couple the electromagnetic waves following their reflection from the coating.  
   
   
       7 ) A coating thickness gauge as claimed in claims  5  wherein the optical fibre comprises a bifurcated optical fibre.  
   
   
       8 ) A coating thickness gauge as claimed in claims  2  wherein the probe head further comprises one or more beam steering elements employed to shape and redirect the electromagnetic waves.  
   
   
       9 ) A coating thickness gauge as claimed in  claim 2  wherein the gauge further comprises a spectrometer arranged to receive the reflected electromagnetic waves.  
   
   
       10 ) A coating thickness gauge as claimed in  claim 1  wherein the probe head locating mechanism comprises a ledge suitable for receiving the can comprising the coating to be tested.  
   
   
       11 ) A coating thickness gauge as claimed  claim 10  wherein the probe head locating mechanism further comprises two rollers connected to one or more roller electric motors wherein the operation of the one or more roller electric motors results in the rollers rotating with the same orientation.  
   
   
       12 ) A coating thickness gauge as claimed in claims  11  wherein the roller electric motor is connected to the two rollers via a first belt located around at least two belt cogs located on a first roller support.  
   
   
       13 ) A coating thickness gauge as claimed in claims  1  wherein the probe head locating mechanism comprises a turn table the rotation of which is controlled by a turn table electric motor.  
   
   
       14 ) A coating thickness gauge as claimed in claims  13  wherein the turn table electric motor is connected to the turn table via a turn table belt.  
   
   
       15 ) A coating thickness gauge as claimed in  claim 13  wherein the turn table further comprises three or more arms mounted upon a first surface of the turn table wherein the three or more arms are resiliently biased towards a centre of the first surface of the turn table.  
   
   
       16 ) A coating thickness gauge as claimed in  claim 15  wherein each of the arms are pivotally mounted upon the first surface of the turn table.  
   
   
       17 ) A coating thickness gauge as claimed in  claim 16  wherein the turn table further comprises a gearing mechanism arranged such that each of the three or more arms rotate with the same orientation and magnitude.  
   
   
       18 ) A coating thickness gauge as claimed in  claim 1  wherein the probe head locating mechanism comprises a first probe electric motor connected to the probe arm wherein the operation of the first probe electric motor results in the probe arm rotating about the longitudinal axis.  
   
   
       19 ) A coating thickness gauge as claimed in  claim 1  wherein the probe head locating mechanism further comprises a probe arm support that connects the probe arm to a mount.  
   
   
       20 ) A coating thickness gauge as claimed  claim 19  wherein the probe head locating mechanism further comprises one or more support rods, the length of which is substantially parallel to the longitudinal axis, and upon which the mount is located.  
   
   
       21 ) A coating thickness gauge as claimed in  claim 20  wherein the probe head locating mechanism further comprises a second probe electric motor connected to the mount wherein the operation of the second probe electric motor controls the position of the probe head along the longitudinal axis.  
   
   
       22 ) A coating thickness gauge as claimed in  claim 21  wherein at least one of the support rods is threaded and the second probe electric motor is connected to the mount via a gear mechanism.  
   
   
       23 ) A coating thickness gauge as claimed in  claim 19  wherein the probe head locating mechanism further comprises a third probe electric motor connected to the probe arm support such that the operation of the third probe electric motor controls the position of the probe head along an axis perpendicular to the longitudinal axis.  
   
   
       24 ) A coating thickness gauge as claimed in  claim 23  wherein the third probe electric motor is connected to the probe arm support via a second belt located around at least two belt cogs located on the mount.  
   
   
       25 ) A coating thickness gauge as claimed in  claim 19  wherein the probe head locating mechanism further comprises a fourth probe electric motor connected to the probe head wherein the operation of the fourth probe electric motor controls the angle of the probe head relative to the longitudinal axis.  
   
   
       26 ) A coating thickness gauge as claimed in  claim 25  wherein the fourth probe electric motor is connected to the probe head via a third belt located around at least two belt cogs located on the probe arm.  
   
   
       28 ) A coating thickness gauge as claimed in  claim 11  wherein the coating thickness gauge further comprises an electronic controller employed to automatically control the electric motors of the probe head locating mechanism.  
   
   
       29 ) A coating thickness gauge as claimed in  claim 28  wherein the electronic controller is also employed to automatically control the spectrometer.